Electrosurgical method and system for treating foot ulcer

ABSTRACT

An electrosurgical method for treating foot ulcer, including diabetic foot ulcer, comprising: positioning an active electrode in close proximity to the ulcer, the active electrode being disposed on a distal end of an electrosurgical shaft; applying a high-frequency voltage potential difference across the active electrode and a return electrode in the presence of an electrically conductive fluid, the voltage potential being sufficient to generate plasma at the active electrode; and stimulating the ulcer with the active electrode to increase blood flow, remove unhealthy tissue and induce the body&#39;s natural healing response.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior application Ser. No.11/327,089, filed Jan. 6, 2006, and entitled “Electrosurgical Method andSystem for Treating Foot Ulcer,” hereby incorporated herein byreference.

FIELD OF INVENTION

This invention pertains to electrosurgical systems for treating ofulcer, in particular, an electrosurgical method of treating diabeticfoot ulcer whereby an active electrode in the presence of plasma isdirected to debride tissue, induce blood flow, and leverage the body'scytokine response to promote healing.

BACKGROUND AND PRIOR ART

An ulcer is a break in a skin or a mucus membrane evident by a loss ofsurface tissue, tissue disintegration, necrosis of epithelial tissue,nerve damage and pus. On patients with long-standing diabetes and withpoor glycemic control, a common condition is diabetic foot ulcer,symptoms of which include surface lesions with peripheral neuropathy,arterial insufficiency, and ischemia of surrounding tissue, deformities,cellulitis tissue formation and inflammation. Cellulitis tissue includescallous and fibrotic tissue. If left untreated a diabetic foot ulcer canbecome infected and gangrenous which can result in disfiguring scars,foot deformity, and/or amputation.

As illustrated in FIG. 1A, a diabetic foot ulcer may develop on areas ofthe foot subjected to pressure or injury such as on the dorsal portionof the toes, the pad of the foot, and the heel. Depending on itsseverity, the condition can vary in size, as illustrated in FIG. 1B,from a small inflammation on the toe with cellulitis and unhealthytissue that extends up to about 10 mm from the center of theinflammation, to a larger neuropathic lesion on the ball of the footcharacterized by cellulitis and unhealthy tissue that extends beyond 2cm of the perimeter of the perimeter. If the ulcer is accompanied byasteomeylitis, deep abscess or critical ischema, the condition maytrigger amputation.

To assist in procedures for treating diabetic foot ulcers, one ofseveral available grading systems such as the Wagner UlcerClassification System shown in Table 1, below, is used to assess theseverity of the ulcer and prescribe treatment. In making the assessment,the ulcer is examined to establish its location, size, depth, andappearance to determine whether it is neuropathic, ischemic, orneuro-ischemic. Depending on the diagnosis, an antibiotic isadministered and if further treatment is necessary, the symptomatic areais treated more aggressively, for example, by debridement of unhealthytissue to induce blood flow and to expose healthy underlying tendons andbone. If warranted, post-debridement treatment such as dressings, foams,hydrocolloids, genetically engineered platelet-derived growth factorbecaplermin and bio-engineered skins and the like are applied.

TABLE 1 Wagner Ulcer Classification System Grade Classification Type ofLesion 0 No open lesion (may have some cellulitis) 1 Superficial(partial or full thickness cellulitis) 2 Ulcer extension to ligament,tendon, joint capsule without abscess or osteomyelitis 3 Deep ulcer withabscess, osteomyelitis, or joint sepsis 4 Gangrene localized to portionof forefoot or heel 5 Extensive gangrenous involvement of the entirefoot

In treating ulcers including diabetic foot ulcers, it has beenrecognized that early intervention to treat affected tissue before alesion breaks out is beneficial, particularly to debride tissue,increase blood flow and stimulate healthy tissue growth. Topicaldebriding enzymes are sometime used but are expensive and have not beenconclusively shown to be beneficial. After the condition has progressedto a lesion with extensive cellulitis, later stage intervention is alsobeneficial if the treatment involves removal of unhealthy tissue,increasing blood flow, and stimulating healthy tissue growth. It istherefore an objective to provide methods and systems to facilitatethese goals.

SUMMARY OF THE INVENTION

In one embodiment, the method is an electrosurgical procedure fortreating ulcer, in particular diabetic foot ulcer, comprising:positioning an active electrode in close proximity to the ulcer, theactive electrode disposed on a distal end of an electrosurgical probe orshaft; and applying a high-frequency voltage potential difference acrossthe active electrode and a return electrode sufficient to generateplasma at the active electrode, and to modify the ulcer. In oneembodiment, an electrically conductive fluid is provided at the activeelectrode. Modification of the ulcer in accordance with the presentmethod include perforating tissue in the vicinity of the ulcer,debriding tissue to increase blood flow, and applying plasma to leveragethe body's natural healing response.

In one embodiment, current is conducted into the ulcer to perforate andremove unhealthy tissue, restore blood flow and promote healing.

In using plasma to modify ulcer, the present method removes unhealthytissue and improve blood flow, and also leverages the body's cytokinerole in coordinating inflammatory response and repairing tissue asdescribed in “Percutaneous Plasma Discetomy Stimulates Repair In InjuredInter-vertebral Discs”, Conor W. O'Neill, et al, Department ofOrthopedic Surgery, Department of Radiology, University of California,San Francisco, Calif. (2004) herein incorporated by reference.

As noted in the O'Neil reference, plasma alters the expression ofinflammatory response in tissue, leading to a decrease in interlukin-1(IL-1) and an increase in interlukin-8 (IL-8). While both IL-1 and IL-8have hyperalgesic properties, Il-1 is likely to be the more importantpathophysiologic factor in pain disorders than IL-8. Also, as describedin the O'Neil reference, cytokines play an important role incoordinating inflammatory and repair response to tissue injury. Forexample, IL-1 is a catabolic mediator that induces proteases andinhibits extra-cellular matrix synthesis. On the other hand, IL-8 isanabolic as it promotes a number of tissue repair functions includingangiogenesis, fibroblast proliferation and differentiation, stem cellmobilization, and maturation and remodeling of matrix. Thus a decreasein IL-1 and an increase in IL-8 suggest that plasma has a role instimulating a healing response mediated by IL-8 to mediate tissuedegeneration, resulting in overall tissue healing, an a decrease ininflammation and pain.

Since the method can be applied at any stage of the condition, themethod can therefore be used to treat ulcerated tissue both before andafter a lesion forms. Hence, both the early stages of the conditionbefore extensive tissue damage have occurred, and at a later stage whenthere is extensive tissue damage and cellulitis can be treated.

Embodiments of the present methods and system are described andillustrated in the following detailed specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration of ulcer locations on a foot.

FIG. 1B is an illustration of a diabetic foot ulcer on the pad of thefoot.

FIG. 2 is an illustration of an electrosurgical system adaptable for usewith the present method.

FIG. 3A is an illustration of an electrode configuration for debridingulcerated tissue in accordance with the present method.

FIG. 3B is an illustration of an electrode configuration for perforatingulcerated tissue in accordance with the present method.

FIG. 4 is an algorithm of an embodiment of the present method.

DETAILED DESCRIPTION

Electrosurgical apparatus and systems adaptable for use with the presentmethod are illustrated and described in commonly owned U.S. Pat. Nos.6,296,638, 6,602,248 and 6,805,130 the disclosure of which is hereinincorporated by reference. In one exemplary embodiment illustrated inFIG. 2, the electrosurgical system (8) includes a probe (10) comprisingan elongated shaft (12) and a connector (14) at its proximal end, andone or more active electrodes (16A) disposed on the distal end of theshaft. Also disposed on the shaft but spaced from the active electrodeis a return electrode (16B). A handle (20) with connecting power cable(18) and cable connector (22) can be removably connected to the powersupply (26).

As used herein, an active electrode is an electrode that is adapted togenerate a higher charge density, and hence generate more plasma,relative to a return electrode when a high-frequency voltage potentialis applied across the electrodes, as described herein. Typically, ahigher charge density is obtained by making the active electrode surfacearea smaller relative to the surface area of the return electrode.

Power supply (26) comprises selection means (28) to change the appliedvoltage level. The power supply (26) can also include a foot pedal (32)positioned close to the user for energizing the electrodes (16A, 16B).The foot pedal (32) may also include a second pedal (not shown) forremotely adjusting the voltage level applied to electrodes (16A, 16B).Also included in the system is an electrically conductive fluid supply(36) with tubing (34) for supplying the probe (10) and the electrodeswith electrically conductive fluid. Details of a power supply that maybe used with the electrosurgical probe of the present invention isdescribed in commonly owned U.S. Pat. No. 5,697,909 which is herebyincorporated by reference herein.

As illustrated in FIG. 2, the return electrode (16B) is connected topower supply (26) via cable connectors (18), to a point slightlyproximal of active electrode. Typically the return electrode is spacedat about 0.5 mm to 10 mm, and more preferably about 1 mm to 10 mm fromthe active electrode. Shaft (12) is disposed within an electricallyinsulative jacket, which is typically formed as one or more electricallyinsulative sheaths or coatings, such as polyester,polytetrafluoroethylene, polyimide, and the like. The provision of theelectrically insulative jacket over shaft (12) prevents directelectrical contact between shaft (12) and any adjacent body structure orthe surgeon. Such direct electrical contact between a body structure andan exposed return electrode (16B) could result in unwanted heating ofthe structure at the point of contact causing necrosis.

As will be appreciated, the above-described systems and apparatus canapplied equally well to a wide range of electrosurgical proceduresincluding open procedures, intravascular procedures, urological,laparoscopic, arthroscopic, thoracoscopic or other cardiac procedures,as well as dermatological, orthopedic, gynecological,otorhinolaryngological, spinal, and neurologic procedures, oncology andthe like. However, for the present purposes the system described hereinis directed to treat various forms of ulcer, including skin ulcer, mucusmembrane ulcer, foot ulcer, cellulitic tissue, and diabetic foot ulcer.

In accordance with the present method, the system of FIG. 2 is adaptableto apply a high frequency (RF) voltage/current to the activeelectrode(s) in the presence of electrically conductive fluid to modifythe structure of tissue on and in the vicinity of the ulcer. Thus, withthe present method, the system of FIG. 2 can be used to modify tissueby: (1) creating perforations in the vicinity of the ulcer; (2)volumetrically removing tissue, including bone and cartilage in thevicinity of the ulcer (i.e., ablate or effect molecular dissociation ofthe tissue structure) from on and around the ulcer; (3) forming holes,channels, divots, or other spaces on the ulcer; (4) cutting or resecttissues of the ulcer; (5) shrinking or contracting collagen-containingconnective tissue in and around the ulcer and/or (6) coagulate severedblood vessels in and around the ulcer.

In accordance with the present method, the applied current can be usedto modify tissue in several ways, e.g., the current can be passeddirectly into the target site by direct contact with the electrodes suchto heat the target site; or the current can be passed indirectly intothe target site through an electrically conductive fluid located betweenthe electrode and the target site also to heat the target site; orcurrent can be passed into an electrically conductive fluid disposedbetween the electrodes to generate plasma for treating the target site.

In accordance with the present method, the high frequency voltagedifference applied between one or more active electrode(s) and one ormore return electrode(s) develop high electric field intensities in thevicinity of the target tissue. The high electric field intensitiesadjacent to the active electrode(s) induces molecular breakdown oftarget tissue by molecular dissociation of tissue components (ratherthan by thermal evaporation or carbonization). In this procedure it isbelieved that the tissue structure is volumetrically removed throughmolecular disintegration of larger organic molecules into smallermolecules and/or atoms, such as hydrogen, oxygen, oxides of carbon,hydrocarbons and nitrogen compounds. This molecular disintegrationcompletely removes the tissue structure, as opposed to dehydrating thetissue material by the removal of water from within the cells of thetissue.

The high electric field intensities is generated, in accordance with thepresent method, by applying a high frequency voltage that sufficient tovaporize electrically conductive fluid disposed over at least a portionof the active electrode(s) in the region between the distal tip of theactive electrode(s) and the target tissue. The electrically conductivefluid may be a liquid, such as isotonic saline, Ringer's lactatesolution, blood and other body fluids delivered to the target site, or aviscous fluid, such as a conductive gel, applied to the target site.Since the vapor layer or vaporized region has relatively high electricalimpedance, it minimizes current flow into the electrically conductivefluid. This ionization, under these conditions, induces the discharge ofplasma comprised of energetic electrons and photons from the vapor layerand to the surface of the target tissue. A more detailed description ofthis phenomenon, termed Coblation™, can be found in commonly assignedU.S. Pat. No. 5,683,366 the complete disclosure of which is incorporatedherein by reference.

In various embodiments of the present method, the electricallyconductive fluid possesses an electrical conductivity value above aminimum threshold level, in order to provide a suitable conductive pathbetween the return electrode and the active electrode(s). The electricalconductivity of the fluid (in units of milliSiemens per centimeter ormS/cm) is usually be greater than about 0.2 mS/cm, typically greaterthan about 2 mS/cm and more typically greater than about 10 mS/cm. In anexemplary embodiment, the electrically conductive fluid is isotonicsaline, which has a conductivity of about 17 mS/cm.

Also in various embodiments of the preset method, it may be necessary toremove, e.g., aspirate, any excess electrically conductive fluid and/orablation by-products from the surgical site. In addition, it may bedesirable to aspirate small pieces of tissue that are not completelydisintegrated by the high frequency energy, or other fluids at thetarget site, such as blood, mucus, and other body fluids.

Accordingly, in various embodiments the present system includes one ormore suction lumen(s) in the shaft, or on another instrument, coupled toa suitable vacuum source for aspirating fluids from the target site. Invarious embodiments, the instrument also includes one or more aspirationelectrode(s) coupled to the aspiration lumen for inhibiting cloggingduring aspiration of tissue fragments from the surgical site. A morecomplete description of these embodiments can be found in commonly ownedU.S. Pat. No. 6,190,381, the complete disclosure of which isincorporated herein by reference for all purposes.

In the present method a single electrode or an electrode array may bedisposed over a distal end of the shaft of the electrosurgicalinstrument to generate and apply the plasma to the tissue. In bothconfigurations, the circumscribed area of the electrode or electrodearray will generally depend on the desired diameter of the perforationsand amount of debriding to be performed. In one embodiment, the area ofthe electrode array is in the range of from about 0.25 mm² to 20 mm²,preferably from about 0.5 mm² to 10 mm², and more preferably from about0.5 mm² to 5.0 mm².

In addition, the shape of the electrode at the distal end of theinstrument shaft will also depend on the size of the surface area to betreated. For example, the electrode may take the form of a pointed tip,a solid round wire, or a wire having other solid cross-sectional shapessuch as squares, rectangles, hexagons, triangles, star-shaped, or thelike, to provide a plurality of edges around the distal perimeter of theelectrodes. Alternatively, the electrode may be in the form of a hollowmetal tube having a cross-sectional shape that is round, square,hexagonal, rectangular or the like. The envelope or effective diameterof the individual electrode(s) ranges from about 0.05 mm to 3 mm,preferably from about 0.1 mm to 2 mm.

Examples of an electrosurgical apparatus that can be used to modifytissue in accordance with the present method are illustrated in FIGS. 3Aand 3B. With reference to FIG. 3A, in one embodiment the apparatuscomprises an active electrode (34) disposed on the distal end of a shaft(36). Spaced from the active electrode is a return electrode (38) alsodisposed on the shaft. Both the active and return electrodes areconnected to a high frequency voltage supply (not shown). Disposed incontact with the active and return electrodes is an electricallyconductive fluid (40). In one embodiment the electrically conductivefluid forms an electrically conductive fluid bridge (42) between theelectrodes. On application of a high frequency voltage across theelectrode, plasma is generated as described above, for use in treatingtissue in accordance with the present method. A more detaileddescription of this phenomenon, termed Coblation™, and the operation ofthe electrode illustrated in FIG. 3A can be found in commonly assignedU.S. Pat. No. 6,296,638 the complete disclosure of which is incorporatedherein by reference. Advantageously, as the tip of the electrode (34)presents a relatively broad surface area, the electrode tip illustratedin FIG. 3A is beneficially used for treating larger ulcers includingdebriding large amounts of dead or necrotic tissue, in accordance withthe present method.

Similarly, with reference to FIG. 3B, in one embodiment the apparatuscomprises an active electrode (44) disposed on the distal end of a shaft(46) Spaced from the active electrode is a return electrode (48) alsodisposed on the shaft. Both the active and return electrodes areconnected to a high frequency voltage supply (not shown). On applicationof a high frequency voltage across the electrode in the presence of aconductive fluid plasma id generated for use in treating tissue inaccordance with the present method. A more detailed description of thisphenomenon, termed Coblation™, and the operation of the electrodeillustrated in FIG. 3B can be found in commonly assigned U.S. Pat. No.6,602,248 the complete disclosure of which is incorporated herein byreference. Advantageously, as the tip of the electrode (34) presents apointed, the electrode tip of FIG. 3B is beneficially used forperforating smaller areas of tissue in the vicinity of the ulcer toinduce blood flow to the tissue.

In a typical procedure involving treatment of diabetic foot ulcer, itmay be necessary to use one or more shapes of electrodes. For example,in a first step, an electrode of the type illustrated in FIG. 3A may beemployed to debride large area of unhealthy tissue surrounding theulcer. Thereafter, an electrode as shown in FIG. 3B can be used toperforate the debrided area to induce blood flow.

The area of the tissue treatment surface can vary widely, and the tissuetreatment surface can assume a variety of geometries, with particularareas and geometries being selected for specific applications. Theactive electrode surface(s) can have area(s) in the range from about0.25 mm² to 75 mm², usually being from about 0.5 mm² to 40 mm². Thegeometries can be planar, concave, convex, hemispherical, conical,linear “in-line” array, or virtually any other regular or irregularshape.

Most commonly, the active electrode(s) or active electrode array(s) willbe formed at the distal tip of the electrosurgical instrument shaft,frequently being planar, disk-shaped, pointed or hemispherical surfacesfor use in reshaping procedures, or being linear arrays for use incutting. Alternatively or additionally, the active electrode(s) may beformed on lateral surfaces of the electrosurgical instrument shaft(e.g., in the manner of a spatula).

The voltage difference applied between the return electrode(s) and thereturn electrode is high or radio frequency, typically between about 5kHz and 20 MHz, usually being between about 30 kHz and 2.5 MHz,preferably being between about 50 kHz and 500 kHz, more preferably lessthan 350 kHz, and most preferably between about 100 kHz and 200 kHz. TheRMS (root mean square) voltage applied will usually be in the range fromabout 5 volts to 1000 volts, preferably being in the range from about 10volts to 500 volts depending on the active electrode size, the operatingfrequency and the operation mode of the particular procedure or desiredeffect on the tissue (e.g., contraction, coagulation, cutting orablation).

Typically, the peak-to-peak voltage for ablation or cutting of tissuewill be in the range of from about 10 volts to 2000 volts, usually inthe range of 200 volts to 1800 volts, and more typically in the range ofabout 300 volts to 1500 volts, often in the range of about 500 volts to900 volts peak to peak (again, depending on the electrode size, theoperating frequency and the operation mode). Lower peak-to-peak voltageswill be used for tissue coagulation or collagen contraction and willtypically be in the range from 50 to 1500, preferably from about 100 to1000, and more preferably from about 120 to 600 volts peak-to-peak

The power source may be current limited or otherwise controlled so thatundesired heating of the target tissue or surrounding (non-target)tissue does not occur. In a preferred embodiments, current limitinginductors are placed in series with each independent active electrode,where the inductance of the inductor is in the range of 10 uH to 50,000uH, depending on the electrical properties of the target tissue, thedesired tissue heating rate and the operating frequency. Alternatively,capacitor-inductor (LC) circuit structures may be employed, as describedpreviously in U.S. Pat. No. 5,697,909, the complete disclosure of whichis incorporated herein by reference. A more detailed description of thisphenomenon, termed Coblation™, can be found in commonly assigned U.S.Pat. No. 5,683,366 the complete disclosure of which is incorporatedherein by reference.

The current flow path between the active electrodes and the returnelectrode(s) may be generated by submerging the tissue site in anelectrically conductive fluid (e.g., a viscous fluid, such as anelectrically conductive gel), or by directing an electrically conductivefluid through a fluid outlet along a fluid path to the target site(i.e., a liquid, such as isotonic saline, or a gas, such as argon). Theconductive gel may also be delivered to the target site to achieve aslower more controlled delivery rate of conductive fluid. In addition,the viscous nature of the gel may allow the surgeon to more easilycontain the gel around the target site (e.g., as compared withcontainment of a liquid, such as isotonic saline). A more completedescription of an exemplary method of directing electrically conductivefluid between active and return electrodes is described in U.S. Pat. No.5,697,281, the contents of which are incorporated by reference herein intheir entirety.

With reference to FIG. 4, the present method in one embodiment is aprocedure for treating ulcers, including skin ulcer, mucus membraneulcers, foot ulcers, a diabetic foot ulcer to promote healing. Inparticular embodiments, the method (50) includes the steps of: (52)positioning an active electrode in close proximity to the ulcer, theactive electrode disposed on a distal end of a shaft; and (54) applyinga high-frequency voltage potential difference across the activeelectrode and a return electrode sufficient to generate plasma at theactive electrode, whereby the ulcer is modified by the active electrode.

In one embodiment, a conductive fluid such as isotonic saline, aconductive gel, Ringer's solution and body fluid such as blood and bodyplasma is preset and is in contact with the active electrode. As notedabove, the conductive fluid in the presence of a sufficientlyhigh-frequency voltage will generate plasma as used in the presentmethod.

In one embodiment, the conductive fluid forms a conductive bridgebetween the active electrode and the return electrode. In thisembodiment, the active and return electrodes are disposed on the distalend of an electrosurgical shaft as described above. Thus in thisembodiment, since current does not pass into the tissue, plasmagenerated in the conductive fluid is used to modify the tissue asdescribed above.

In an alternative embodiment, an electrically conductive fluid layer isprovided in between the active electrode and the tissue, in the vicinityof the tissue. In this embodiment, in addition to plasma generated inthe fluid, current from the applied high frequency voltage is appliedinto the tissue. Thus with this embodiment, both current and plasma areused to modify the tissue. In one embodiment the applied high frequencyvoltage is adjusted to provide sufficient current for coagulating andsealing the tissue and stop bleeding.

In various embodiments of the method, a suitably configured activeelectrode is used to treat the ulcer, for example, by debriding,perforating, inducing blood-flow to tissue, coagulating tissue andvolumetrically removing tissue in the vicinity of the ulcer. Thus, forexample, an active electrode as schematically illustrated in FIG. 3A andcomprised of a relatively wide distal end can be used to debride andvolumetrically remove unhealthy tissue in the vicinity of the ulcer.Thereafter, in accordance with the present method, the smaller activeelectrode schematically illustrated in FIG. 3B can be used to perforatethe tissue in the debrided area to cause blood flow for healing.

In use, the active electrode is translated axially and radially over thetissue in the proximity of the ulcer to modify the tissue. Depending onthe size of the debrided area and the lesion, small wounds can betreated by a needle-type active electrode as illustrated in FIG. 3Bwherein many perforations are applied on the ulcer in a random manner,whereas for cellulitis in the vicinity of the ulcer, the perforationsmay be applied in a grid-like manner. For larger and more complicatedulcers, an electrode with a wider tip as illustrated in FIG. 3A can beused for more aggressive treatment.

In various embodiments, the tissue in the vicinity of the ulcer istreated with the active electrode for about 0.5 seconds at a time.Depending on the size of the area to be treated the method in oneembodiment involves perforating the tissue at about 2 to 5 mm apart inthe vicinity of the ulcer to form perforations with diameters of up toabout 3 mm, and about 3 mm to 5 mm in depth.

In both types of electrode configurations, an electrically conductivefluid is provided to generate plasma. Depending on the apparatus used,the conductive fluid is provided by a lumen that discharges the fluid inthe vicinity of the tissue. Similarly, in alternate embodiments, asuction lumen is provided to suction fluid and body tissue from thevicinity of the ulcer.

While the invention is described with reference to the Figures andmethod herein, it will be appreciate by one ordinarily skilled in theart that the invention can also be practiced with modifications withinthe scope of the claims. The scope of the invention therefore should notbe limited to the embodiments as described herein, but is limited onlyby the scope of the appended claims.

1. An electrosurgical method of treating ulcer tissue, comprising:positioning an active electrode in close proximity to the ulcer, theactive electrode disposed on a distal end of a shaft; delivering anelectrically conductive liquid proximate the active electrode; andapplying a high-frequency voltage potential difference across the activeelectrode and a return electrode in the presence of the electricallyconductive liquid sufficient to form a plasma at the active electrode,whereby the plasma formed at the active electrode modifies the ulcertissue and promotes the healing of the ulcer tissue.
 2. The method ofclaim 1, wherein the voltage potential difference is sufficient tovaporize the electrically conductive liquid.
 3. The method of claim 1,wherein the ulcer tissue comprises skin ulcer tissue.
 4. The method ofclaim 1, wherein the ulcer tissue comprises mucus membrane ulcer tissue.5. The method of claim 1, wherein the ulcer tissue comprises foot ulcertissue.
 6. The method of claim 1, wherein the ulcer tissue comprisesdiabetic foot ulcer tissue.
 7. The method of claim 1, wherein the ulcertissue comprises cellulitic tissue.
 8. The method of claim 1, wherebymodifying the ulcer tissue comprises directing the plasma to the ulcertissue.
 9. The method of claim 1, wherein modifying the ulcer tissue isselected from the group consisting of debriding, perforating, inducingblood-flow to, coagulating, and volumetrically removing at least aportion of the ulcer tissue.
 10. The method of claim 9, furthercomprising debriding, perforating, inducing blood-flow to, coagulating,and volumetrically removing at least a portion of the tissue in thevicinity of the ulcer tissue.
 11. The method of claim 1, wherebypositioning the active electrode comprises translating the activeelectrode across the ulcer tissue.
 12. The method of claim 1, whereinthe active electrode and the return electrode are disposed on the shaft.13. The method of claim 2, wherein the plasma is generated from thevaporized electrically conductive liquid.
 14. The method of claim 1,wherein the electrically conductive liquid forms a conductive bridgebetween the active electrode and the return electrode.
 15. The method ofclaim 1, wherein the electrically conductive liquid is selected from thegroup consisting of body fluid, conductive gel, isotonic saline, andRinger's lactate.
 16. The method of claim 1, including contacting atleast a portion of the ulcer tissue with the active electrode.
 17. Themethod of claim 1, further comprising submerging the ulcer tissue withthe conductive liquid.
 18. The method of claim 1, further comprisinglimiting the application of the high-frequency voltage potentialdifference for a selected time period.
 19. The method of claim 9,wherein perforating the ulcer tissue comprises forming a plurality ofperforations in the ulcer tissue and in the vicinity of the ulcertissue, the plurality of perforations spaced less than 5 mm apart. 20.The method of claim 9, wherein perforating the ulcer tissue comprisesforming a plurality of perforations with diameters of up to about 3 mmin the ulcer tissue and in the vicinity of the ulcer tissue.
 21. Themethod of claim 9, wherein perforating the ulcer tissue comprisesforming a plurality of perforations up to about 3 mm in depth in the inthe ulcer tissue and in the vicinity of the ulcer tissue.
 22. The methodof claim 9, wherein perforating the ulcer tissue comprises forming aplurality of perforations up to about 5 mm in depth in the ulcer tissueand in the vicinity of the ulcer tissue.
 23. The method of claim 1,further comprising adjusting the voltage to cause coagulation of atleast portions of ulcer tissue and at least portions of tissue in thevicinity of the ulcer tissue.
 24. The method of claim 1, wherein theactive electrode is attached to a high-frequency voltage supply and aconductive liquid supply.
 25. The method of claim 1, wherein the activeelectrode is selected from the group consisting of an electrode having apointed tip, a wire electrode, a screen electrode, and a suctionelectrode.
 26. The method of claim 1, wherein the shaft comprises asuction lumen.
 27. The method of claim 1, wherein the shaft comprises aliquid delivery lumen.
 28. An electrosurgical method of treating ulcertissue, comprising: positioning an active electrode in close proximityto the ulcer tissue, the active electrode disposed on a distal end of ashaft; delivering a non-gaseous electrically conductive fluid inproximity to the active electrode; and applying a high-frequency voltagepotential difference across the active electrode and a return electrodein the presence of the non-gaseous electrically conductive fluidsufficient to form a plasma at the active electrode, whereby the plasmaformed at the active electrode modifies the ulcer tissue and promotesthe healing of the ulcer tissue.